Stable oscillators



STABLE OSCILLATORS Filed May 7, 1958 INVENTOR. JAMES 6. DA v/s, J2.

BY/i/M ATTOQNEY United States harem G 2,978,650 5 and a selectedinductance L L or L is connected in the grid return path between thegrid of V-l and ground. STABLE OSCILLATORS Switch means S-Z effects theselection of an individual James Davis, Carlisle, -s assigllol t0Raytheon inductance to cover a particular band of frequencies. p y, acorporation of Delaware The motion of switch means 8-2 is preferablyganged Filed May 7, 1958 Ser. No. 733,643 10 vivrietlslitlhgat of S1 asindicated by the dotted line in the 4 Claims. (Cl. 331-144) A thirddischarge device, V-3, is driven from the resonant circuit to providethe output signal. The plateof V-3 is connected through a resistor 20 tothe DC. potential source, and the cathode is connected to ground ThePresent invention relates generally to electronic through seriallyconnected resistors 22 and 24. The inoscillator apparatus, and moreParticularly to a p of put grid of we is returned to the junction ofresistors oscillator wherein a resonant tank circuit is coupled to 22and 24 through resistor 26 Input Condenser 28 an electronic circuitarrangement in such manner that couples the resonant i i to the i f V 3It i the pulses of energy necessary to maintain oscillations in to benoted a condenser 23 should be f small mthe t nk C r t re derived fromtW0 discharge devices tude to provide loose coupling from the resonantcircuit Which have a multivibrator pactioll- The to the output stage ofV-3 so as to minimize damping multivibrator action is in turnsynchronized from the or pulling of h ill i generator utpuL A hoscillatory Wave Of The tank Circuit, in that the tank same time, gridreturn resistor 26 should be sufficiently Provides the energy t0 triggerthe multivibrator into a large in magnitude so that the combination ofcondenser Successive Cycle of Operation 28 and resistor 26 does not actto differentiate the input A primary object of the present invention isto produce wavef r a a stable generator of substantially sinusoidalwaveform Di h d i V 3 i operated as a th d f ll wer oscillations. withthe output waveform taken across the cathode lead A further object ofthe invent on s to P de a resistors through a coupling condenser 30connected to alaxation type oscillator capable of sustainingoscillations 30 fir t Output i l 31 A second output t mi l 34. is byitself, but which is maintained extremely stable in freconnected to thecathode follower output by way of aquency and amplitude by the aid of afrequency conresistor 36. This second output terminal is optionallytrolling tank circuit which is coupled to the oscillator in i l d d s ast provide a additional output wave a novel fashion. having acharacteristic similar to that obtainable from 'Another object of thepresent in e is w Provide terminal 32 for operation of a countingdevice. a multi-band variable frequency oscillator having im- Inoperation of this invention resistance element 14 proved amplitudestability with changing frequency within provides the bias for electrondischarge devices V-1 and any one band and between one band and anotherby V-2. When oscillation occurs in this invention the oscilutilizingcathode follower techniques to minimize load- 40 latory signal builds upin amplitude until the negative ing of the frequency determining tankcircuit of the grid swing of the oscillatory signal cuts off dischargedeoscillator. vice V-l. The cathode of discharge device V-i is held Amore specific object of the present invention is to positive by thecurrent flowing in discharge device V-Z provide a one-shotcathode-coupled multivibrator waveand the resistance element 14. formgenerator in which an LC tank circuit maintains a When discharge deviceV-l is substantially cut off as' stable frequency output which iscoupled through a cathode follower stage to obtain an output sine waveshape exceedingly free of distortion.

The above and further objects, advantages and details of the inventionwill become readily apparent to those skilled in the art uponconsideration of the detailed description of a preferred embodimentthereof which follows, reference being made to the single figure of theaccompanying drawing. 7

Two electron discharge devices V-l and V-Z are-provided. The plate ofV-1 is connected through a re sistor 10 to a source of DC. energizingpotential'which may be stabilized to the indicated value of +150 voltsfunction as a grounded-grid amplifier having a cathode input and a plateoutput.

A resonant circuit consisting of a variable condenser C described abovethe gain of discharge device V-l ap-' proaches zero and this limits theamplitude of the oscillations. Due to discharge device V-l being cut offby the negative peak, the wave form impressed upon resistance element 14will be a sinusoid with the negative peak flattened or cut off. Inasmuchas discharge devices .V-1 and V-2 are broad band amplifiers withoutreactance in the range of frequencies employed in this invention, thecutoff of discharge device V4 and therefore the amplitude of theoscillations will be independent of the frequency.

The function of resistance elements R-i, R-2 or"R3 is to selectivelydecouple the tank circuit from the plate of discharge device V-Z,thereby minimizing the effects of parameter changes in discharge deviceV-E on the tank circuit comprising the inductance and capacitance.

Utilizing the well-known theory of cathode followers, that no gridcurrent is drawn by discharge device V-l, the effect of parameterchanges inside discharge device 1 on the tank circuit is also minimized.Because of this minimizing eifect of the parameter changes the frequencyof this oscillator is a function only of the tank circuit inductance andcapacitance. The stability of the oscillator is therefore effectively afunction of the sta- 70 bility of the components L and C.

The wave shape in the tank circuit is a pure sine wave. The bias ofdischarge device V-3 is such that V-3 operby means of a gas dischargevoltage regulator tube according to known practice. The plate of V-2 isconnected through a resistor 12 to the same potential source.

1 The cathodes of V-l and V-2 are interconnected and a 4 common cathoderesistor 14 connects their junction point to ground.

A feed back condenser 16 is selectively coupled from the plate of V-2 tothe grid of V-1 through switch means 8-1. An adjustable resistancemember R R or R is included in this feed back path for a purpose whichwill be further explained hereinafter. Grid 18 of V-2 is grounded, sothat this right-hand tube of the multivibrator pair may be considered insome respects to ates linearly over the entire wave shape and the outputof V-3 is a pure sine wave. As noted above, the wellknown theory ofcathode followers indicates that the effects of V-3 on the tank circuitwill also be minimal, as were the eifects of V4.

Various modifications of the embodiment shown in the drawing may be madewithoutafiecting the scope of the present invention, as will occur tothose skilled in the art. For example, the discharge devices V4 and V-i.may be combined in a single envelope, and device V-3 which is.illustrated as being a triode-connected tetrode may be any othermulti-grid tube operated as a triode, or may be a triode if desired.Alternatively, the vacuum tube discharge devices may be replaced withtheir transistor equivalents according to known theories of duality.Also, in certain applications where the oscillation frequency rangepermits, the LC resonant circuit may be replaced by equivalent meanssuch as piezo crystal or cavity resonator.

Accordingly, the foregoing description is to be taken by way ofillustration only, and not as limiting the practice of the invention,which should be interpreted according to the scope of the appendedclaims.

I claim:

1. A periodic waveform generator including a pair of electron dischargedevices each having a grid, a cathode and an anode, a source of anodepotential having one terminal connectedto said anodes and a-secondterminal connected to ground, a common cathode bias resistor to limitgrid current flow and to further provide a first feedback path havingone terminal connected to said cathodes and a second terminal connectedto ground, a capacitor and a resistor connected in seriesinterconnecting the anode of one electron discharge device and the gridof the other discharge device to provide a second feedback path, meansconnecting the grid of said one electron discharge device directly toground, and a resonant frequency determining circuit connecting the gridof said other electron discharge device to ground.

2. A periodic Waveform generator including a pair of electron dischargedevices each having a grid, a cathode and an anode, a source of anodepotential having one terminal connected to said anodes and a secondterminal connected to ground, a common cathode bias resistor to limitcurrent flow and to further provide a first feedback path having oneterminal connected to said cathodes and a second terminal connected toground, a capacitor and a resistor connected in series interconnectingthe anode of one electron discharge device and the grid of the otherdischarge device to provide a second feedback path, means connecting thegrid of said one electron discharge device directly to ground, aresonant frequency determining circuit connecting the grid of said otherelectron discharge device to ground, and output wave shaping meansconnected to the grid of said other electron discharge device.

3. A waveform generator comprising in combination two electron dischargedevices, said devices each having a cathode, an anode and at least onegrid, a direct cur- Y aarspao rent source, individual impedance meansconnected between the anode of each device and the positive terminal ofsaid source, an impedance common to said cathodes connected between saidcathodes and the negative terminal of said source, circuit meansincluding a resistor in series with a condenser connected between theanode of one of said devices and a grid of the other device, a directconnection between a grid of said one device and the negative terminalof said source, a resonant circuit connected between a grid of saidother device and the negative terminal of said source, and output waveshaping means loosely coupled to the grid of said other device.

4. A frequency stable sine wave generator including an electrondischarge network comprising a first electron discharge device havingcathode, grid and anode electrodes, a second electron discharge devicehaving cathode, grid and anode electrodes, resistors connected to theanode electrodes of said devices, a capacitor and resistor connected in'series interooupling the grid of said first device and the anode of saidsecond device, a direct connection between the grid of said seconddevice and ground, means to connect the positive pole of a source ofdirect current potential to said anode resistors and to connect thenegative pole of said source to ground, a connection between thecathodes of both of said devices, a coupling resistor connected betweensaid cathode connection and ground, said coupling resistor having avalue normally at which said second device is rendered conducting andsaid first device is blocked due to current flow of said conductingsecond device, a resonant circuit connected between the grid electrodeof said first device and ground toperiodically render the first deviceconducting and block said second device at the resonant frequency ofsaid resonant circuit to sustain sine wave oscillations, at thirdelectron discharge device having cathode, grid and anode electrodes, aresistor connected between the anode of said third device and thepositive pole of said source of direct current, a coupling capacitorconnected from the grid of said first device to the grid of said thirddevice for providing loose coupling from the resonant'circuit to saidthird device, a cathode resistor connected from the cathode of saidthird device to ground, and a grid resistor connected from the grid ofsaid third device to intermediate the ends of said cathode resistor,said grid resistor having a value so that the combination of said gridresistor and said coupling capacitor does not act to differentiate aninput signal to the grid of said third device.

References Cited in the file of this patent UNITED STATES PATENTS2,269,417 Crosby Ian. 6, 1942 2,423,304 Fitch July 1, 1947 2,514,087Phelan July 4, 1950 2,553,165 Bliss May 15, 1951 2,610,298 ZaloudekSept. 9, 1952 2,846,584 Hurst Aug. 5, 1958

